A traditional voice telephone network typically includes a circuit-switched network to establish communications between a sender and a receiver. The circuit-switched network is a type of network in which a communication circuit (path) for a call is set-up and dedicated to the participants in that call. For the duration of the connection, all resources on that circuit are unavailable for other users. An Electronic Worldwide Switch Digital (EWSD) is a widely-installed telephonic switch system. Common Channel Signaling System No. 7 (i.e., SS7 or C7) is a global standard for telecommunications defined by the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T). The standard defines the procedures and protocol by which network elements in the public switched telephone network (PSTN) exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup, routing and control.
A softswitch is a software-based entity that provides call control functionality. The various elements that make a softswitch architecture network include a call agent, which is also known as a media gateway controller or softswitch. The network also includes a media gateway, a signaling gateway, a feature server, an applications server, a media server, and management, provisioning and billing interfaces.
The softswitch architecture does not replace an SS7 architecture. For example, when a person wants to setup a call from one location to another location, the person picks up the phone at one location and dials a series of numbers. A local switch recognizes the call as a long distance call, which is then forwarded to a long haul exchange where it is recognized as an out of state call. Then, the call is transferred to a national gateway for the other location. The call makes a hop to an intermediate gateway, which is located somewhere between the two locations, and finally the call goes through two or three switches before it connects to a local switch associated with the number. The role of SS7, which does not use traditional trunks, is to ensure, prior to actually setting up the call, there is a clear path from end to end. Only when there is sufficient resources is the call set-up.
The major difference between a softswitch architecture and a traditional architecture is that the call is not required to pass through as many smaller switches. Today, when the person makes a trunk call the person uses the whole trunk even though a smaller portion of the available bandwidth is required. On the other hand, with a softswitch architecture, an Internet protocol (IP) connection between the gateways of the two locations is established and a switching fabric between the two locations is in the form of fiber optic lines or other form of trunk. There is no need to reserve trunks and set-up is not required. One only has to reserve the bandwidth that the call will need.